Source/drain junction formation

ABSTRACT

A device includes a first channel region and a first gate structure formed over the first channel region. A first source/drain region is adjacent the first channel region and the first source/drain region includes a crystalline structure doped with a first dopant. A first silicide is formed over the first source/drain region. The first source/drain region includes a first concentration of the first dopant between 2.0×10 21  atoms per centimeter cubed and 4.0×10 21  atoms per centimeter cubed at a depth of 8 to 10 nanometers. A gradient of decreasing concentration of the first dopant is one decade for every 5.5 to 7.5 nanometers deeper than the first concentration.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a continuation of U.S. patent application Ser. No.14/056,711, entitled, “Source/Drain Junction Formation,” filed on Oct.17, 2013, which application is hereby incorporated herein by reference.

BACKGROUND

Semiconductor devices are used in a large number of electronic devices,such as computers, cell phones, and others. Semiconductor devicescomprise integrated circuits that are formed on semiconductor wafers bydepositing many types of thin films of material over the semiconductorwafers, and patterning the thin films of material to form the integratedcircuits. Integrated circuits include field-effect transistors (FETs)such as metal oxide semiconductor (MOS) transistors.

One of the goals of the semiconductor industry is to continue shrinkingthe size and increasing the speed of individual FETs. To achieve thesegoals, fin FETs (FinFETs) or multiple gate transistors are used in sub32 nm transistor nodes. FinFETs not only improve areal density, but alsoimprove gate control of the channel.

Unfortunately, as FinFETs become smaller and smaller, the processingsteps used to fabricate the FinFETs may produce undesirable andunintended consequences. For example, the method of forming the sourceand drain regions in a FET or a FinFET may negatively impact the deviceor the device yield.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 is a perspective view of a basic FinFET device having portionscut away for the purpose of illustration;

FIG. 2 is a cross section of the basic FinFET device of FIG. 1 takengenerally along line x-x;

FIGS. 3-8 collectively illustrate an embodiment process flow for forminga source/drain region for a FinFET;

FIGS. 9-13 collectively illustrate an embodiment process flow forforming a source/drain region for a FinFET;

FIG. 14 is a graph illustrating the concentration of phosphorusdetermined using secondary ion mass spectrometry (SIMS);

FIG. 15 is a graph illustrating the concentration of phosphorusdetermined using SIMS; and

FIG. 16 is a series of images obtained by a transmission electronmicroscope (TEM).

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the present embodiments are discussed in detailbelow. It should be appreciated, however, that the present disclosureprovides many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative, and do not limit the scope of the disclosure.

The present disclosure will be described with respect to embodiments ina specific context, namely a FinFET metal oxide semiconductor (MOS). Theconcept may also be applied, however, to other integrated circuits andelectronic structures including, but not limited to, a planarfield-effect transistor (FET), a multiple gate field-effect transistor(MuGFET), and nanowire devices.

FIGS. 1-2 represent a FinFET 10 in accordance with an embodiment, whichwill be briefly described. The FinFET 10 includes a substrate 12supporting several fins 14, which are at least partially embedded inisolation regions 16. In an embodiment, the isolation regions 16comprise shallow trench isolation (STI) regions. The substrate 12 may beformed from bulk silicon, silicon, germanium, silicon germanium, asilicon-containing material, silicon-on-insulator (SOI), or anothersuitable semiconductor material. In an embodiment, the semiconductorsubstrate 12 is a p-type substrate.

The fins 14 generally extend between source/drain regions 18 of theFinFET 10. The fins 14 may be formed from, for example, silicon,germanium, silicon germanium, a silicon-containing material, or anothersuitable fin material. The gate electrode structure 22 of FIGS. 1-2 mayinclude several discrete layers or components such as, for example, aninterfacial oxide layer, a high-k-dielectric layer, and a metal gatelayer. Spacers 20, which are stacked upon a portion of the fins 14adjacent the source/drain regions 18 and may be formed from a nitride(e.g., Si₃N₄), are disposed on opposing sides of a gate electrodestructure 22 depicted in FIG. 2. As discussed below, source/drainregions 18 are formed having an ultra shallow junction. One of thechallenges in forming an ultra shallow junction (e.g., a p-n junction)in the source/drain region of a device is minimizing the sheetresistance (Rs) for a given junction depth (Xj). Embodiments of theprocess disclosed herein permit formation of the ultra shallow junctionwhile providing a suitably low sheet resistance.

As will be more fully explained below, FIGS. 3-8 collectively illustratean embodiment process flow for forming a source/drain region in an NMOSFinFET device and FIGS. 9-13 collectively illustrate an embodimentprocess flow for forming a source/drain region in an PMOS FinFET device.The process flows described herein may be also be used to formsource/drain regions in other semiconductor devices (e.g., a planar FET,a MuGFET, etc.).

As shown in FIG. 3, recesses 30 are formed in a substrate 32. As will bemore fully explained below, the recesses 30 represent areas where sourceand drain regions of the device will eventually be formed. In anembodiment, the recesses 30 may be formed through, for example, anetching or other suitable process. As shown, portions of the substrate32 between the recesses 30 may be protected by, for example, aprotective feature 31 such as, for example, a dummy gate, a mask, aresist, spacers, and so on. In other words, the protective feature 31protects what will eventually be the channel region of the device.

The substrate 32 may be formed from bulk silicon, silicon, germanium,silicon germanium, a silicon-containing material, silicon-on-insulator(SOI), or another suitable semiconductor material. In an embodiment, thesemiconductor substrate 32 is either a p-type substrate or an n-typesubstrate and may include one or more p-type or n-type wells therein.

Referring now to FIGS. 3-4, an n-type semiconductor material 34 isformed in the recesses 30 using an epitaxy process. In an embodiment,the n-type semiconductor material comprises silicon phosphorous (SiP).In an embodiment, the n-type semiconductor material comprises siliconphosphorous having a concentration of less than about 1×10²⁰ atoms percentimeter cubed to about 7×10²⁰ atoms per centimeter cubed.

Thereafter, and as shown in FIG. 5, a pre-amorphization doping of then-type semiconductor material 34 is performed using helium (He) and aplasma doping (PLAD) 36. As used herein, the pre-amorphization dopingmay be referred to as a pre-amorphization implant (PAI). In anembodiment, the plasma doping of the helium may act as or provide abuffer layer to retard or prevent post-plasma doping diffusion of aphosphorous dopant, which will be discussed below.

In an embodiment, the plasma doping 36 of the helium is performed at anenergy of between about 0.4 kiloelectron-volts (keV) about 1.0kiloelectron-volts. In an embodiment, the plasma doping 36 of the heliumis performed using a variable energy to prevent bubble defects in then-type semiconductor material 34. Bubble defects, which are undesirablepockets of gas in the semiconductor material 34, may occur if, forexample, a depth of the doping is too great (e.g., greater than about 10to 20 nm) and the doping energy remains constant.

By way of example, the energy of the plasma doping 36 may be linearlyincreased from 0.4 kiloelectron-volts (keV) to about 1.0kiloelectron-volts, linearly decreased from 1.0 kiloelectron-volts (keV)to about 0.4 kiloelectron-volts, or otherwise varied during the dopingprocess. In an embodiment, a dose of the helium is between about1.0×10¹⁶ atoms per centimeter squared and about 2.0×10¹⁶ atoms percentimeter squared.

In an embodiment, a concentration of the helium in the n-typesemiconductor material 34 after the doping by plasma doping 36 isbetween about ten percent to about 60 percent of the PLAD dose.

Next, as shown in FIG. 6, a doping of phosphorous (P) into the n-typesemiconductor material 34 is performed using plasma doping 38 in orderto form a source/drain region 40. In an embodiment, phosphorus is dopedin the n-type semiconductor material 34 utilizing about 0.5% PH₃ andabout 99.5% H₂. In an embodiment, the plasma doping 38 of thephosphorous is performed at a constant energy of between about 2kiloelectron-volts (keV) and about 10 kiloelectron-volts (keV). Thephosphrous (P) plasma doping may be performed with or without pre PLADHe amorphization doping.

In an embodiment, the plasma doping 38 of the phosphorous is performedwith a variable energy to prevent bubble defects in the n-typesemiconductor material 34. In an embodiment, the plasma doping 38 of thephosphorous is performed with a variable energy of about 5kiloelectron-volts (keV) to about 3 kiloelectron-volts (keV). In anembodiment, the plasma doping 38 of the phosphorous is performed with avariable energy of about 6 kiloelectron-volts (keV) to about 4kiloelectron-volts (keV). The energy of the plasma doping 36 may belinearly increased from 3 kiloelectron-volts (keV) to about 5kiloelectron-volts, linearly decreased from 6 kiloelectron-volts (keV)about 4 kiloelectron-volts, or otherwise varied during the dopingprocess.

In an embodiment, a dose of the phosphorus is between about 1×10¹⁶ atomsper centimeter squared to 2×10¹⁶ atoms per centimeter squared. In anembodiment, a collective process time of the plasma doping 36 in FIG. 5and the plasma doping 38 of FIG. 6 is less than about thirty (30)seconds.

After the phosphorus doping 38 has been performed , a silicide layer 42is formed over the source/drain region 40 as shown in FIG. 7. In anembodiment, a high K loop and an OLD loop process are performed beforethe silicide layer 42 is formed. However, for the sake of brevity, theseprocesses have not been illustrated or explained in detail. In anembodiment, the silicide layer 42 has a depth of about eight to abouttwelve nanometers. The silicide layer 42 may have other depths in otherembodiments or in other devices.

In an embodiment, a concentration of the phosphorus in the source/drainregion 40 beneath the silicide layer 42 is between about 2.0 ×10²¹ atomsper centimeter cubed and about 4.0×10²¹ atoms per centimeter cubed. Inother words, the concentration of the phosphorus at the interface of thebottom surface of the silicide layer 42 and top surface of theunderlying source/drain material 34 is between about 2.0×10²¹ atoms percentimeter cubed and about 4.0×10²¹ atoms per centimeter cubed.

After the silicide layer 42 has been formed, an anneal process isperformed. As will be more fully explained below, the anneal processpermits portions of the source/drain regions 40 damaged during doping tobe recrystallized or repaired.

In an embodiment, the anneal process comprises a millisecond anneal. Inan embodiment, the millisecond anneal is performed using a laser anneal(LSA), at a temperature of about 900° C. to about 1200° C., and for atime of about 10 microseconds (μs) to about 2 milliseconds (ms). In anembodiment, the millisecond anneal is performed using a flash anneal(uSSA), at a temperature of about 700° C. to about 1000° C., and for atime of about 0.8 ms to about 5 ms.

In an embodiment, the anneal process comprises a microwave anneal.Microwave annealing of layers in semiconductors is an application ofthermal processing of semiconductors, with low processing temperatureeliminating unwanted diffusion as one of the potential advantages. In anembodiment, the microwave anneal is performed using a free carrierabsorption technique. In an embodiment, the microwave anneal isperformed using a dipolar polarization or/and interfacial polarizationheating. In an embodiment, the microwave anneal is performed at atemperature of about 300° C. to about 600° C., and for a time of about30 seconds to about 300 seconds.

In an embodiment, the pre-amorphization doping permits the annealprocess to be performed at a relatively low temperature such as, forexample, between about 400° C. to about 600° C. Notably, when thepre-amorphization doping process is employed a more defect rich areawill be formed, which will enhance the microwave reaction with the dopedarea.

Thereafter, the protective feature 31 (e.g., the dummy gate) of FIG. 7may be removed using a conventional removal process and then replacedwith the metal gate or a gate electrode structure 46 as shown in FIG. 8using a conventional gate formation process. As shown in FIG. 8, thegate electrode structure 46 and the spacers 44 are disposed over fins 48adjacent the source/drain regions 40 to form a channel in the FinFET 50.

Those skilled in the art will recognized that further or additionalprocessing steps may be taken to form the FinFET 50 of FIG. 8. Inaddition, the FinFET 50 of FIG. 8 may contain or include additionalmaterials, features, and layers in different embodiments.

Referring now to FIGS. 9-13, an embodiment process flow for forming asource/drain region for a FinFET is collectively illustrated. Theprocess flow may be also be used to form source/drain regions in othersemiconductor devices (e.g., a planar FET, a MuGFET, etc.). As shown inFIG. 9, recesses 60 are formed in a substrate 62. As will be more fullyexplained below, the recesses 60 represent areas where source and drainregions of the device will eventually be formed. In an embodiment, therecesses 60 may be formed through, for example, an etching or othersuitable process. As shown, portions of the substrate 62 between therecesses 60 may be protected by, for example, a protective feature 61such as, for example, a dummy gate, a mask, a resist, and so on. Inother words, the protective feature 61 protects what will eventually bethe channel region of the device.

The substrate 62 may be formed from bulk silicon, silicon, germanium,silicon germanium, a silicon-containing material, silicon-on-insulator(SOI), or another suitable semiconductor material. In an embodiment, thesemiconductor substrate 62 is either a p-type substrate or an n-typesubstrate and may include one or more p-type or n-type wells therein.

Referring now to FIGS. 9-10, a p-type semiconductor material 64 isformed in the recess 60 using an epitaxy process. In an embodiment, thep-type semiconductor material comprises silicon germanium boron (SiGeB).

Thereafter, as shown in FIG. 11, a pre-amorphization doping boron (B)and helium (He) into the p-type semiconductor material 64 is performedsimultaneously using plasma doping 66 to form a source/drain region 68.In an embodiment, the boron comprises B₂H₆. In an embodiment, the dopingof boron and helium comprises about 0.3% to about 5% B₂H₆ and about 95%to about 99.7% helium. In an embodiment, the doping of boron and heliumcomprises about 0.5% B₂H₆ and about 99.5% helium.

In an embodiment, the plasma doping 66 of the boron and helium isperformed at an energy of between about 0.4 kiloelectron-volts (keV) andabout 0.6 kiloelectron-volts. In an embodiment, a dose of the boron isabout 4.5×10¹⁶ atoms per centimeter squared. In an embodiment, a processtime of the plasma doping 66 in FIG. 11 is less than about fifteen (15)seconds.

After the plasma doping 66 has been performed, a silicide layer 70 isformed over the source/drain region 40 as shown in FIG. 12. In anembodiment, the silicide layer 70 has a depth of about eight to abouttwelve nanometers. The silicide layer 70 may have other depths in otherembodiments or in other devices.

In an embodiment, a concentration of the boron in the source/drainregion 68 beneath the silicide layer 70 is between about 3.0×10¹⁵ atomsper centimeter cubed and about 1.0×10¹⁶ atoms per centimeter cubed.

After the silicide layer 70 has been formed, an anneal process isperformed. As will be more fully explained below, the anneal processpermits portions of the source/drain regions 64 damaged during doping tobe recrystallized or repaired.

In an embodiment, the anneal process comprises a millisecond anneal. Inan embodiment, the millisecond anneal is performed using a laser anneal(LSA), at a temperature of about 900° C. to about 1200° C., and for atime of about 10 microseconds (μs) to about 2 milliseconds (ms). In anembodiment, the millisecond anneal is performed using a flash anneal(uSSA), at a temperature of about 700° C. to about 1000° C., and for atime of about 0.8 ms to about 5 ms.

In an embodiment, the anneal process comprises a microwave anneal. In anembodiment, the microwave anneal is performed using a free carrierabsorption technique. In an embodiment, the microwave anneal isperformed using a dipole resonance heating. In an embodiment, themicrowave anneal is performed at a temperature of about 300° C. to about600° C., and for a time of about 30 seconds to about 300 seconds.

In an embodiment, the pre-amorphization doping permits the annealprocess to be performed at a relatively low temperature such as, forexample, between about 400° C. to about 600° C. Notably, when thepre-amorphization doping process is employed a more defect rich areawill be formed, which will enhance the microwave reaction with the dopedarea.

Thereafter, the protective feature 61 (e.g., the dummy gate) of FIG. 12may be removed using a conventional removal process and then replacedwith the metal gate or a gate electrode structure 80 as shown in FIG. 13using a conventional gate formation process. As shown in FIG. 13, thegate electrode structure 76 and the spacers 74 are disposed over fins 78adjacent the source/drain regions 64 to form a channel in the FinFET 80.

Those skilled in the art will recognized that further or additionalprocessing steps may be taken to form the FinFET 80 of FIG. 13. Inaddition, the FinFET 80 of FIG. 13 may contain or include additionalmaterials, features, and layers in different embodiments.

In an embodiment, the process depicted in FIGS. 9-13 may be performed inaddition to the process depicted in FIGS. 3-8 in order to form a devicewith both PMOS and NMOS transistors. In an embodiment, the process ofFIGS. 9-13 may be performed first, followed by the process of FIGS. 3-8.In another embodiment, the process of FIGS. 3-8 may be performed first,followed by the process of FIGS. 9-13.

Referring now to FIG. 14, a graph 90 illustrating the concentration ofphosphorus, which is determined using secondary ion mass spectrometry(SIMS), is provided. As a practical matter, the peak dopingconcentration of the phosphorous is measured at a depth below thesurface (e.g., about 8-12 nanometers) to minimize surface noise effects.

As shown in FIG. 14, the chart includes four curves representing thephosphorus concentration (Y-axis) relative to the depth of thesource/drain (X-axis). As shown, each of the curves was produced usingan energy or bias of 2 kV. Two of the curves were produced using a “LoPAI” while the other two curves were produced using a “Hi PAI”. As usedherein, the Lo PAI means a dose of helium of 1.0×10¹⁶ atoms percentimeter squared and the Hi PAI means a dose of helium above thatamount. Continuing, two of the curves were produced where no clean wasperformed, while the other two curves were produced after a clean of thesurface of the source/drain region was performed.

As is well known in the art, the dose of the phosphorus retained in thesilicon is lower than the dose of the phosphorus doped in the silicon(e.g., 1.0×10¹⁶ atoms per centimeter squared). For the illustrateddoping conditions in FIG. 14, the dose of the phosphorus retained in thesource/drain was calculated from the curves to be 3.67×10¹⁵ atoms percentimeter squared, 3.85×10¹⁵ atoms per centimeter squared, 1.1×10¹⁵atoms per centimeter squared, and 1.13×10¹⁵ atoms per centimetersquared.

Still referring to FIG. 14, when the process conditions were Hi PAI, 2kV bias, a dose of 1.0×10¹⁶ atoms per centimeter squared, with no cleanand no anneal, the junction depth at a phosphorus concentration of5×10¹⁸ atoms per centimeter cubed was measured to be 19.5 nanometers. Inthis context, junction depth refers to the junction between thephosphorous and boron (not shown) at 5×10¹⁸ atoms per centimeter cubed.Notably, the junction depth could have been measured at other phosphorusconcentrations. Indeed, the point is simply to make all measurements atthe same concentration to provide a consistent reference point forcomparison purposes.

As shown in FIG. 14, the abruptness (abr) of the junction was found tobe 3.5 nanometers per decade. In other words, the slope of the curve atthe phosphorus concentration of 5×10¹⁸ atoms per centimeter squared was3.5 nanometers per decade.

When the process conditions were Lo PAI, 2 kV bias, a phosphorus dose of1.0×10¹⁶ atoms per centimeter squared, with no clean and no anneal, thejunction at a phosphorus concentration of 5×10¹⁸ atoms per centimetersquared was measured to be 19.7 nanometers. In addition, the abruptnessof the junction was found to be 2.8 nanometers per decade.

When the process conditions were Hi PAI, 2 kV bias, a phosphorus dose of1.0×10¹⁶ atoms per centimeter squared, with a clean and an anneal, thesheet resistance was measured at 406.24 ohms per square centimeter andthe junction at a phosphorus concentration of 5×10¹⁸ atoms percentimeter squared was measured to be 25 nanometers. In addition, theabruptness of the junction was found to be 5.5 nanometers per decade.

When the process conditions were Lo PAI, 2 kV bias, a phosphorus dose of1.0×10¹⁶ atoms per centimeter squared, with a clean and an anneal, thesheet resistance was measured at 381.94 ohms per square centimeter andthe junction at a phosphorus concentration of 5×10¹⁸ atoms percentimeter squared was measured to be 28 nanometers. In addition, theabruptness of the junction was found to be 7.6 nanometers per decade. Asthe measurements show, a desirable abruptness at the junction can beachieved using the embodiment process disclosed herein.

In an embodiment, the desired concentration of phosphorus was betweenabout 1.0×10²¹ atoms per centimeter cubed and about 5.0×10²¹ atoms percentimeter cubed at a depth of about eight nanometers to about tennanometers. As the graph 90 of FIG. 14 illustrates, the actualconcentration of phosphorus was between about 1.0×10²¹ atoms percentimeter cubed and about 3.0×10²¹ atoms per centimeter cubed at adepth of about eight nanometers to about ten nanometers when a processsimilar to that depicted in FIGS. 3-8 was employed to form thesource/drain regions. As illustrated in FIG. 14, even after the cleanand anneal steps have been performed a suitably abrupt junction (abr) ofeither 5.5 nanometers per decade or 7.6 nanometers per decade isachieved.

By generating a concentration of phosphorous within the desired range ata depth of about 8-10 nanometers into the source/drain region after thesilicide layer has been formed, the source/drain resistance is desirablyor beneficially reduced. As noted above, the depth of 8-10 nanometers ischosen to mitigate surface noise effects, corresponds to the depth ofthe silicide, and corresponds to a location of the Schottky barrier atthe junction of the silicide and the underlying doped source/drainmaterial. In an embodiment, the source/drain resistance is reducedbetween about 30% to about 70% percent. As can be seen in FIG. 8 andFIG. 13, where the source/drain epitaxy 34/64 protrudes higher than atop surface of the substrate, the silicide 42/70 can be formed higherthan the top surface of the substrate. Consequently, at least a portionof the junction can also be formed higher than the top surface of thesubstrate.

Referring now to FIG. 15, another graph 92 illustrating theconcentration of phosphorus is provided. Similar to FIG. 14, the graph92 includes several curves representing the phosphorus concentration(Y-axis) relative to the depth of the source/drain (X-axis). As shown,each of the curves was produced using an energy or bias of 2 kV or 4 kV.In addition, the curves reflect using either a Hi PAI or Lo PAI,employing a clean or not, and employing an anneal or not. For theillustrated doping conditions in FIG. 15, the dose of the phosphorusretained in the source/drain was calculated from the curves to be3.67×10¹⁵ atoms per centimeter squared, 3.85×10¹⁵ atoms per centimetersquared, 8.73×10¹⁵ atoms per centimeter squared, 8.66×10¹⁵ atoms percentimeter squared, 1.1×10¹⁵ atoms per centimeter squared, 1.13×10¹⁵atoms per centimeter squared, 2.1×10¹⁵ atoms per centimeter squared, and1.87×10¹⁵ atoms per centimeter squared. As shown in FIG. 15, the curvesillustrate that, depending on the process conditions chosen, a suitableabruptness (abr) at a phosphorus concentration of between about 1.0×10²²atoms per centimeter cubed and about 5.0×10²¹ atoms per centimeter cubedand a junction depth at about 8-10 nanometers is achievable.

In an embodiment, the desired concentration of phosphorus was betweenabout 1.0×10²¹ atoms per centimeter cubed and about 5.0×10²¹ atoms percentimeter cubed at a depth of about eight nanometers to about tennanometers. As the graph 92 illustrates, the actual concentration ofphosphorus was between about 1.0×10²¹ atoms per centimeter cubed andabout 3.0×10²¹ atoms per centimeter cubed at a depth of about eightnanometers to about ten nanometers when a process similar to thatdepicted in FIGS. 3-8 was employed to form the source/drain regions.

Referring now to FIG. 16, a series of images 94 obtained by atransmission electron microscope (TEM) are provided. As will be morefully explained below, the image 94 a illustrates an image of thesource/drain region in an intermediate stage of formation where damageis still present. The corresponding image 94 b illustrates thesource/drain region after the damage in the image 94 a has been repairedby the anneal process Likewise, the image 94 c illustrates an image ofthe source/drain region in an intermediate stage of formation wheredamage is still present. The corresponding image 94 d illustrates thesource/drain region after the damage in the image 94 c has been repairedby the anneal process. The anneal process is able to provide the fullrecrystalline recovery in the images 94 b, 94 d because the embodimentdoping processes described herein were employed.

Still referring to FIG. 16, the process conditions for the top leftimage were an energy of 2 kV, a phosphorus dose of 1.0×10¹⁶ atoms percentimeter squared, a Hi PAI, with no clean and no anneal. The processconditions for the top right image were an energy of 2 kV, a phosphorusdose of 1.0×10¹⁶ atoms per centimeter squared, a Lo PAI, with no cleanand no anneal.

The process conditions for the bottom left image were an energy of 2 kV,a phosphorus dose of 1.0×10¹⁶ atoms per centimeter squared, a Hi PAI,with a clean and an anneal. The process conditions for the bottom rightimage were an energy of 2 kV, a phosphorus dose of 1.0×10¹⁶ atoms percentimeter squared, a Lo PAI, with a clean and an anneal. In contrast tothe top two images, which illustrate damage, the bottom two imagesillustrate a full recrystalline recovery when embodiment processes asdisclosed herein are used. In other words, a full recrystallization maybe achieved by way of the anneal.

From the foregoing, with regard to the process depicted in FIGS. 3-8 and9-13, it should be recognized that the plasma doping of the helium mayact as a buffer layer to retard or prevent post-plasma dopingphosphorous dopant diffusion. In addition, the phosphorus dopantabruptness of less than about three nanometers per decade may beretained, as shown in FIGS. 14-15.

In addition, when the plasma doping of the phosphorous is performedafter the PAI plasma doping of the helium, the energy and dose may betuned to achieve a desired phosphorous concentration at a desired depthto provide a source/drain resistance (Rcsd) reduction after silicideformation. For example, the phosphorous concentration may be betweenabout 2.0×10²¹ atoms/cm³ and about 4.0×10²¹ atoms/cm³ at a depth ofbetween about eight nanometers to about twelve nanometers into thesource/drain region after the silicide layer has been formed forsuitable or desirable source/drain resistance reduction.

With regard to the process depicted in FIGS. 9-13, it should berecognized that a fast doping time (e.g., under 15 seconds) may beachieved by simultaneously doping the boron and the helium. In addition,an abrupt junction of less than about 0.5 nanometers per decade may beachieved, which fulfills the short channel effect (SCE) requirement.Further, an ion gain performance of between about 3-5% may be realized.

One embodiment is a device including a first channel region and a firstgate structure formed over the first channel region. A firstsource/drain region is formed on either side of the first channel regionand the first source/drain region includes a defect-free crystallinestructure doped with a first dopant. A first silicide is formed over thefirst source/drain region. The first source/drain region includes afirst junction and a concentration of the first dopant at the firstjunction is between 2.0×10²¹ atoms per centimeter cubed and 4.0×10²¹atoms per centimeter cubed at a depth of 8 to 10 nanometers. A gradientof decreasing concentration of the first dopant is one decade for every5.5 to 7.5 nanometers of the first source/drain region deeper than thefirst junction.

Another embodiment is a semiconductor device including a first gateformed over a substrate and a first source/drain region formed onopposing sides of the first gate. The first source/drain region includesan epitaxial semiconductor material doped with a first impurity at afirst concentration, where the first impurity is a p-type impurity. Thefirst source/drain region has a first portion formed within thesubstrate. A first silicide is formed on the first source/drain regionand has a thickness of 8 to 10 nm. A second concentration of the firstimpurity at a first interface of the first silicide and firstsource/drain region is between 3.0×10¹⁵ atoms per centimeter cubed and1.0×10¹⁶ per centimeter cubed. A gradient of a concentration of thefirst impurity in the first source/drain region decreases at about 1decade per 0.5 nm depth into the first source/drain region from thefirst interface.

Another embodiment is a semiconductor device including a substrate, afirst gate formed over the substrate, first source/drain regions formedon either side of the first gate within the substrate, a second gateformed over the substrate, and second source/drain regions formed oneither side of the second gate within the substrate. The firstsource/drain regions are doped with a first dopant and the secondsource/drain regions are doped with a second dopant. A first junction inthe first source/drain regions is formed at a depth of 8 to 10 nm, wherea concentration of first dopant at the first junction is between2.0×10²¹ atoms per cm³ and 4.0×10²¹ atoms per cm³. The concentration offirst dopant decreases deeper into the first source/drain regions fromthe first junction at a first abruptness, where the first abruptnesscorresponds to one decade concentration for every 5.5 to 7.5 nm. Asecond junction in the second source/drain regions is formed at a depthof 8 to 10 nm, where a concentration of second dopant at the secondjunction is between 3.0×10¹⁵ atoms per cm³ and 1.0×1016 atoms per cm³.

One embodiment is a device including a first channel region and a firstgate structure formed over the first channel region. A firstsource/drain region is formed on either side of the first channel regionand the first source/drain region includes a defect-free crystallinestructure doped with a first dopant. A first silicide is formed over thefirst source/drain region. The first source/drain region includes afirst junction and a concentration of the first dopant at the firstjunction is between 2.0×10²¹ atoms per centimeter cubed and 4.0×10²¹atoms per centimeter cubed at a depth of 8 to 10 nanometers. A gradientof decreasing concentration of the first dopant is one decade for every5.5 to 7.5 nanometers of the first source/drain region deeper than thefirst junction.

Another embodiment is a semiconductor device including a first gateformed over a substrate and a first source/drain region formed onopposing sides of the first gate. The first source/drain region includesan epitaxial semiconductor material doped with a first impurity at afirst concentration, where the first impurity is a p-type impurity. Thefirst source/drain region has a first portion formed within thesubstrate. A first silicide is formed on the first source/drain regionand has a thickness of 8 to 12 nm. A second concentration of the firstimpurity at a first interface of the first silicide and firstsource/drain region is between 3.0×10¹⁵ atoms per centimeter cubed and1.0×10¹⁶ per centimeter cubed. A gradient of a concentration of thefirst impurity in the first source/drain region decreases at about 1decade per 0.5 nm depth into the first source/drain region from thefirst interface.

Another embodiment is a semiconductor device including a substrate, afirst gate formed over the substrate, first source/drain regions formedon either side of the first gate within the substrate, a second gateformed over the substrate, and second source/drain regions formed oneither side of the second gate within the substrate. The firstsource/drain regions are doped with a first dopant and the secondsource/drain regions are doped with a second dopant. A first junction inthe first source/drain regions is formed at a depth of 8 to 10 nm, wherea concentration of first dopant at the first junction is between2.0×10²¹ atoms per cm³ and 4.0×10²¹atoms per cm³. The concentration offirst dopant decreases deeper into the first source/drain regions fromthe first junction at a first abruptness, where the first abruptnesscorresponds to one decade concentration for every 5.5 to 7.5 nm. Asecond junction in the second source/drain regions is formed at a depthof 8 to 12 nm, where a concentration of second dopant at the secondjunction is between 3.0×10¹⁵ atoms per cm³ and 1.0×10¹⁶ atoms per cm³.

An embodiment method of forming a source/drain region for a transistoris provided. The method includes forming a recess in a substrate andepitaxially growing a semiconductor material in the recess. The methodalso includes amorphizing the semiconductor material and doping thesemiconductor material with a dopant to form the source/drain region.

An embodiment method of forming a source/drain region for a transistorincludes forming a recess in a substrate, epitaxially growing asemiconductor material in the recess, performing a pre-amorphizationdoping of the semiconductor material using a first plasma doping, anddoping the semiconductor material with phosphorus using a second plasmadoping to form the source/drain region.

An embodiment method of forming source/drain regions includes forming arecess in a substrate, epitaxially growing a semiconductor material inthe recess, a doping the semiconductor material with boron and heliumusing plasma doping to form the source/drain region.

While the disclosure provides illustrative embodiments, this descriptionis not intended to be construed in a limiting sense. Variousmodifications and combinations of the illustrative embodiments, as wellas other embodiments, will be apparent to persons skilled in the artupon reference to the description. It is therefore intended that theappended claims encompass any such modifications or embodiments.

What is claimed is:
 1. A device, comprising: a first channel region; afirst gate structure over the first channel region; a first source/drainregion adjacent the first channel region, wherein the first source/drainregion comprises a crystalline structure doped with a first dopant; anda first silicide formed over the first source/drain region, wherein thefirst source/drain region comprises a first concentration of the firstdopant at a first depth of 8 to 10 nm between 2.0×10²¹ atoms per cm³ and4.0×10²¹ atoms per cm³, wherein a gradient of decreasing concentrationof the first dopant is one decade for every 5.5 to 7.5 nm deeper thanthe first depth.
 2. The device of claim 1, wherein the first dopant isan n-type impurity.
 3. The device of claim 1, wherein the first silicidehas a thickness of 8 to 10 nm.
 4. The device of claim 3, wherein thefirst depth corresponds to an interface between the first source/drainregion and the first silicide.
 5. The device of claim 1, furthercomprising: a second channel region; a second gate structure formed overthe second channel region; a second source/drain region adjacent thesecond channel region, wherein the second source/drain region comprisesa crystalline structure doped with a second dopant different than thefirst dopant; and a second silicide formed over the second source/drainregion, wherein the second source/drain region comprises a secondconcentration of the second dopant at a second depth of 8 to 10 nmbetween 3.0×10¹⁵ atoms per cm³ and 1.0×10¹⁶ per cm³, wherein a gradientof decreasing concentration of the second dopant is about one decade forevery 0.5 nm deeper than the second depth.
 6. The device of claim 5,wherein the second dopant is a p-type dopant.
 7. The device of claim 5,wherein the second depth corresponds to an interface between the secondsource/drain region and the second silicide.
 8. The device of claim 1,wherein a concentration of first dopant at the first depth is a peakconcentration of the first dopant in the first source/drain region. 9.The device of claim 1, wherein at least a portion of the first depth isvertically above a topmost point of the first channel region.
 10. Asemiconductor device, comprising: a first gate over a substrate; a firstsource/drain region adjacent the first gate, the first source/drainregion comprising an epitaxial semiconductor material doped with a firstimpurity at a first concentration, the first impurity being a p-typeimpurity; and a first silicide on the first source/drain region, thefirst silicide having a thickness of 8 to 10 nm, wherein a secondconcentration of the first impurity at a first interface of the firstsilicide and first source/drain region is between 3.0×10¹⁵ atoms per cm³and 1.0×10¹⁶ per cm³, wherein a gradient of a concentration of the firstimpurity in the first source/drain region decreases at about 1 decadeper 0.5 nm depth from the first interface.
 11. The semiconductor deviceof claim 10, wherein the first source/drain region is in a fin of a FinField Effect transistor (FinFET).
 12. The semiconductor device of claim10, wherein the first impurity is boron.
 13. The semiconductor device ofclaim 10, wherein the epitaxial semiconductor material of the firstsource/drain region is substantially repaired of defects.
 14. Thesemiconductor device of claim 10, wherein the first source/drain regionhas a second portion that protrudes above the substrate, wherein aportion of the first interface is above the substrate.
 15. Thesemiconductor device of claim 10, further comprising: a second gate overthe substrate; a second source/drain region adjacent the second gatecomprising an epitaxial semiconductor material doped with a secondimpurity at a third concentration, the second impurity being an n-typeimpurity; and a second silicide formed on the second source/drainregion, the second silicide having a thickness of 8 to 10 nm, wherein afourth concentration of the second impurity at a second interface of thesecond silicide and the second source/drain region is between 2.0×10²¹atoms per cm³ and 4.0×10²¹ atoms per cm³, wherein a gradient of aconcentration of the second impurity in the second source/drain regiondecreases at 1 decade per 5.5 to 7.5 nm depth from the second interface.16. The semiconductor device of claim 15, wherein the second impurity isphosphorous.
 17. A semiconductor device comprising: a substrate; a firstgate over the substrate; a first source/drain adjacent the first gate,the first source/drain doped with a first dopant; a second gate formedover the substrate; a second source/drain adjacent the second gate, thesecond source/drain doped with a second dopant; a first concentration offirst dopant in the first source/drain, the first concentration being ata depth of 8 to 10 nm, wherein a concentration of first dopant at thefirst concentration is between 2.0×10²¹ atoms per cm³ and 4.0×10²¹ atomsper cm³, wherein the concentration of first dopant decreases deeper fromthe first concentration at a first abruptness, wherein the firstabruptness corresponds to one decade concentration for every 5.5 to 7.5nm; and a second concentration in the second source/drain, the secondconcentration being at a depth of 8 to 10 nm, wherein a concentration ofsecond dopant at the second concentration is between 3.0×10¹⁵ atoms percm³ and 1.0×10¹⁶ atoms per cm³.
 18. The semiconductor device of claim17, further comprising: a first silicide formed over the firstsource/drain, the first silicide having a thickness of 8 to 10 nm; and asecond silicide formed over the second source/drain, the second silicidehaving a thickness of 8 to 10 nm.
 19. The semiconductor device of claim18, wherein the first concentration corresponds to an interface betweenthe first silicide and the first source/drain, and wherein the secondconcentration corresponds to an interface between the second silicideand second source/drain.
 20. The semiconductor device of claim 17,wherein the concentration of second dopant decreases deeper from thesecond concentration at a second abruptness, wherein the secondabruptness corresponds to about one decade concentration for every 0.5nm.